<?php
/**
 * Created by PhpStorm.
 * User: 刚
 * Date: 2017/8/1
 * Time: 11:39
 */

abstract class OnTheBookShelf
{
    abstract function getBookInfo($previousBook);

    abstract function getBookCount();

    abstract function setBookCount($new_count);

    abstract function addBook($oneBook);

    abstract function removeBook($oneBook);
}